I'm not going to lie, this submission has room for improvement. I know these aren't the most exciting implementations of these concepts and mechanics. I unlocked my concept for the set very late and only was able to come up with a few cards before submissions were due. But I like the glimpse of what could be in this set concept.
-Nich

Which set are you pitching?

Ankh-Theb

What is the name of your pitch?

The Fertile Land

What are the major mechanical themes in the set according to your vision?

1.) Ankh is a supertype that is referenced in the set by spells and effects. Each color uses it differently. It’s most unique feature in this set is that effects count even in the graveyard. That should give it a sufficient afterlife feel.
2.) Eternal Servitude’s flavor is lesser souls of the Plane returning after death to serve the more powerful. It uses the rules created by Morph (minus the ability to flip face up).
3.) Retrace is the returning mechanic. It’ll have a fortune-telling hieroglyph flavor this go around. The twist is that it’ll also be on permanents.
4.) Enemy color theme. Dictated by the flavor of the setting, I see strong reasons to include multicolor enemy colors.

Present a booster pack (10 commons, 3 uncommons, and 1 rare or mythic rare) that shows off the set as well as possible. These cards need not be original designs; previous challenges and other people's ideas are fair game.

Foretold Victory 1R (Common)
Sorcery
Creatures you control get +1/+0 and gain haste until end of turn.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Public Knowledge U (Common)
Instant
Each player draws a card.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Descendant from Greatness W (Common)
Enchantment — Aura
Enchant creature
Enchanted creature gets +1/+1.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Wheatfield Mummy 1WB (Common)
Ankh Creature — Zombie 2/3
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Reedbraid Cranes 1UU (Common)
Ankh Sorcery
Put a 2/2 blue Bird creature token with flying onto the battlefield.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Taskmaster’s Tomb (Common)
Land
2, T, Sacrifice Taskmaster’s Tomb: Search your library for a basic land card and put it onto the battlefield tapped. Then shuffle your library.
Eternal servitude (When this permanent is put into a graveyard from the battlefield face up, return it the battlefield face down as a 2/2 creature.)

Serpent God’s Prayer 5G (Uncommon)
Ankh Sorcery
Put a 1/1 green Snake creature token onto the battlefield for each ankh permanent you control and each ankh card in your graveyard.

Caravan Harrier 1RR (Uncommon)
Ankh Creature – Viashino Warrior 1/1
Haste
When Caravan Harrier enters the battlefield, target creature gets +X/+0 until end of turn, where X equals the number of ankh permanents you control plus the number of ankh cards in your graveyard.
At the beginning of the end step, return Caravan Harrier to its owner’s hand.

Harvester Anubis 2GG (Rare)
Ankh Creature — Hound Shaman 3/3
Other creatures you control get +1/+1 and have eternal servitude.(When a creature with eternal servitude dies face-up, return it to the battlefield face down as a 2/2 creature.)
G, Tap an untapped face down creature you control: Harvester Anubis gets +3/+3 until end of turn.

1) I think Eternal Servitude is a really fascinating take on a Wither/Undying variant.
2) Ankh strikes me as a terribly parasitic mechanic. It would be easy to plug into Eternal Servitude instead by using colorless creatures.
3) A more technical quibble: for a pack-pitch, 5 retrace cards is probably more than needed.
4) I'm not entirely convinced having two "return from the grave" mechanics for permanents in the same set (retrace and eternal servitude) is wise.
5) Between retrace, eternal servitude and the way you use Ankh, this feels like a graveyard set, and I'm not clear if this was your goal (and making on the heels of Innistrad is not all that tempting to me).
6) Ankh creatures with retrace or eternal servitude seem to conflict pretty badly with the ankh-in-graveyard theme.

There are many interesting designs (the retrace sorceries in particular), but I'm not sure they transmit the themes you intended to transmit (cf. the "graveyard set" feel). For examples, retrace doesn't exactly screams "fertileness" to me (but I might be in the minority there), and the enemy color themes doesn't come through at all.

I like Retrace as a way to represent both cyclical fertility and undeath, and there's definitely-probably some design space left to explore there. Finding compelling effects that aren't "this is why we don't do Buyback" is a priority.

Addercoil Staff is very clever.

It seems like if we could find a cohesive way of saying "Ankh cards on your side of the table", Ankh would be more promising, but as is, sure. It's parasitic and I don't really get what it *means* (as opposed to something like Arcane being "the spirit side of things"), but it's space to play around in.

Eternal Servitude is interesting, but less intriguing than retraceable permanents in my book.

There are some interesting ideas in this set, although very heavily built around both the graveyard and eternal servitude seems to heavily lean into morph, to the extent that Harvester of Souls appears to offer virtual immortality to any creature with morph.

I think irrigation ditch is a very clever design around retrace, although I wonder whether it's meant to be designed so that even though it enters tapped, I can still return for coloured mana on the turn it enters. Feels a little counter intuitive for a dual land.

As for Ankh, my only though is that its unclear why certain spells are ankh and others aren't. Is there a reason why Wheatfield Mummy is Ankh but afterworld servent isn't?

Thanks for the comments, gang! I appreciate it quite a bit. Here are my candid responses to you all.

RE: Circeus
1.) My biggest concern with Eternal Servitude would be how many cards with it would be appropriate for the set, and how much depth does it have as a mechanic. (Do free 2/2's matter?)
2.) Ankh is parasitic(linear), but that's fine because both Eternal Servitude and Retrace are modular. Every successful set has a mix of both because they appeal to different types of players.
3.) 5 Retrace is way, way, more than I needed, I think the set would probably have 10-15 retrace cards, if that.
4. and 5.) it's a graveyard set, but the twist is that many of the cards do their work from the graveyard and stay there. It could be too graveyard focued though. So I think it could feel very different from Odyssey or Innistrad.
6.) I'm not sure what to do with Ankh yet, I'll get into it below. As for the enemy color, mechanically, there are stronger links between enemy colors than I could see in ally colors. Eternal Servitude seems primary Black, with secondary in green and white. Retrace on spells seems very Blue and Red. but that may not be as clear to others as it is to me.

RE: Pasteur
I think Retrace has more than enough depth for a Core Set or a standalone set like we're making.

Ankh is flavor-wonky right now, but I have faith it could be given a very clever identity that makes it at least as obvious as Snow permanents, or Arcane spells. I like the mechanical possibilities, and have faith in the flavor. (I puposely used the word Ankh because it's in the name of the plane.)

I agree that retraceble permanents are more promise than eternal servitude. Interesting that neither work with tokens at all. I wouldn't hate a token-light set, btw.

RE: Antny223
I think an Egyptian-themed set should have a heavy graveyard/recycling focus. I had a hard time not designing in that direction. For a while I had a sort of reversed Delve mechanic before I realized I needed to include a returning mechanic and added Retrace (which I think is the most successful part of the submission).

Harvester Annubis's combo with Morph creatures will be fun for casual formats down the road. I'm not sure that interaction should be a concern. Does WotC playtest for older formats?

I'm not sure if new players will hate using up their land drop for a dual land, the way they famously hated losing 1 life. But the interaction of bouncing them the turn you play them for c or D was intentional. These duals would be a classic case of Strategic Complexity, where they reward a player who knows how to best use them, without frustrating newer players.

Ankh needs work. How does each color use the supertype, why are some spells ankh and others aren't. It's tough even for WotC though, if you look at Coldsnap, you may have trouble remembering which cards are snow permanents. Artic Shelf or Arctic Nishoba? Rimewind Cryomancer or Rimefeather Owl? Karplusan Strider or Ohran Yeti? I didn't get a chance to crack the flavor and mechancial guidelines, but I could see that process as being a lot of fun during a full set design.